Spring hinge



FIG. 1 is a front elevational view of a spring hinge showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a bottom front perspective view thereof;

FIG. 4 is a bottom rear perspective view thereof;

FIG. 5 is a top rear perspective view thereof; and,

FIG. 6 is a top front perspective view thereof. 

The ornamental design for a spring hinge, as shown. 